Starship Asterisk*

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Tiny Tethys

Tethys may not be tiny by normal standards, but when it is captured alongside Saturn, it can't help but seem pretty small.

Even Saturn's rings appear to dwarf Tethys (660 miles, or 1,062 kilometers across), which is in the upper left of the image, although scientists believe the moon to be many times more massive than the entire ring system combined.

This view looks toward the unilluminated side of the rings from about 18 degrees below the ringplane. The image was taken in green light with the Cassini spacecraft wide-angle camera on Aug. 19, 2012.

The view was acquired at a distance of approximately 1.5 million miles (2.4 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 63 degrees. Image scale is 86 miles (138 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

owlice wrote:
WOW!!!!

What's the nearly perfect circle on Saturn below the ring shadows? Artifact?

• Shadow of Mimas Time to clean your screen

http://www.latinospost.com/articles/7380/20121126/pac-man-space-thermal-distribution-saturn-moon.htm wrote:
Pac-Man In Space: Thermal Distribution Of Saturn Moon Tethys Resembles Arcade Character
By Keerthi Chandrashekar, Nov 26, 2012

[img3="Scientists with NASA's Cassini mission have spotted two features shaped like the 1980s video game icon "Pac-Man" on moons of Saturn. One was observed on the moon Mimas in 2010 and the latest was observed on the moon Tethys.
(Photo : NASA/JPL-Caltech/GSFC/SWRI)"]http://images.latinospost.com/data/imag ... .jpg?w=600[/img3]

<<For most people Pac-Man conjures up an old video game and arcade joysticks. For some, however, Pac-Man is an astronomical phenomenon. For the second time ever, scientists have now identified a 'Pac-Man' visual in space on Saturn's moon Tethys.

The visual is a thermal image of Tethys, and a look at it shows that the surface temperature's distribution resembles Pac-Man. The first Pac-Man in space observed was a thermal image of another Saturn moon, Mimas, back in 2010.

"Finding a second Pac-Man in the Saturn system tells us that the processes creating these Pac-Men are more widespread than previously thought," said lead author of the study Carly Howett. "The Saturn system -- and even the Jupiter system -- could turn out to be a veritable arcade of these characters." The scientists involved in the discovery were associated with NASA's Cassini mission. The Cassini mission launched in 1997 to study the Saturn system as well as nearby Jupiter.

The Pac-Man thermal distribution gives scientists an insight into the structural makeup of icy moons. According to the study, the Pac-Man thermal distribution is caused by the fact that electrons bombard the forward face of the moon (towards Saturn) at low latitudes. This causes the surface of the moon to turn into hard ice, and take longer to heat up and cool down. The hard ice usually ends up being a different temperature than the surrounding geography.

"Studies at infrared wavelengths give us a tremendous amount of information about the processes that shape planets and moons," said Mike Flasar, the spectrometer's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md. "A result like this underscores just how powerful these observations are.">>

neufer wrote:Pac-Man In Space: Thermal Distribution Of Saturn Moon Tethys Resembles Arcade Character
Latinos Post, by Keerthi Chandrashekar, Nov 26, 2012

[url=http://www.jpl.nasa.gov/spaceimages/details.php?id=pia16198][b][i]A Pair of 'Pac-Men'[/i][/b][/url] [b][i](Credit: NASA/JPL-Caltech/GSFC/SWRI)[/i][/b]

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You could call this "Pac-Man, the Sequel." Scientists with NASA's Cassini mission have spotted a second feature shaped like the 1980s video game icon in the Saturn system, this time on the moon Tethys. (The first was found on Mimas in 2010). The pattern appears in thermal data obtained by Cassini's composite infrared spectrometer, with warmer areas making up the Pac-Man shape.

"Finding a second Pac-Man in the Saturn system tells us that the processes creating these Pac-Men are more widespread than previously thought," said Carly Howett, the lead author of a paper recently released online in the journal Icarus. "The Saturn system - and even the Jupiter system - could turn out to be a veritable arcade of these characters."

Scientists theorize that the Pac-Man thermal shape on the Saturnian moons occurs because of the way high-energy electrons bombard low latitudes on the side of the moon that faces forward as it orbits around Saturn. The bombardment turns that part of the fluffy surface into hard-packed ice. As a result, the altered surface does not heat as rapidly in the sunshine or cool down as quickly at night as the rest of the surface, similar to how a boardwalk at the beach feels cooler during the day but warmer at night than the nearby sand. Finding another Pac-Man on Tethys confirms that high-energy electrons can dramatically alter the surface of an icy moon. Also, because the altered region on Tethys, unlike on Mimas, is also bombarded by icy particles from Enceladus' plumes, it implies the surface alteration is occurring more quickly than its recoating by plume particles.

"Studies at infrared wavelengths give us a tremendous amount of information about the processes that shape planets and moons," said Mike Flasar, the spectrometer's principal investigator at NASA's Goddard Space Flight Center in Greenbelt, Md. "A result like this underscores just how powerful these observations are."

Scientists saw the new Pac-Man on Tethys in data obtained on Sept. 14, 2011, where daytime temperatures inside the mouth of Pac-Man were seen to be cooler than their surroundings by 29 degrees Fahrenheit (15 kelvins). The warmest temperature recorded was a chilly minus 300 degrees Fahrenheit (90 kelvins), which is actually slightly cooler than the warmest temperature at Mimas (about minus 290 degrees Fahrenheit, or 95 kelvins). At Tethys, unlike Mimas, the Pac-Man pattern can also be seen subtly in visible-light images of the surface, as a dark lens-shaped region. This brightness variation was first noticed by NASA's Voyager spacecraft in 1980.

"Finding a new Pac-Man demonstrates the diversity of processes at work in the Saturn system," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Future Cassini observations may reveal other new phenomena that will surprise us and help us better understand the evolution of moons in the Saturn system and beyond."